cast bullet questions

[Dusty Bannister]

Consider following the suggestions to increase the alloy casting temperature. The less tin and antimony the higher the casting temperature needs to be to get best mold fill out (to a point) but not so hot that you cause excessive dross from the oxides of tin and antimony. Adding one percent of tin would help with the flow of the alloy into the mold and might be key in getting better mold fill out. Consider making only one correction at a time and let the temperature stabilize and then cast long enough to get the mold up to correct casting temperature. This will help you find what factor improves your product.

You are also making a mistake when you test the alloy hardness the day after casting with a low antimony alloy. It might take up to three weeks for the final hardness to stabilize. If your castings are measuring a hardness of 9 BHN after 24 hours, it will probably be more like 11 or perhaps a little more when mature. Be patient.

When you measure the diameter of your casting, are you using a micrometer or a caliper? Do you measure at the same location on each bullet or perhaps just the maximum or minimum diameter? I hope you try to use a micrometer and take the reading on the same driving band on either side of the mold parting seam and at 90 degrees from the seam. That can tell you a lot about the casting, and the mold condition.

To avoid the frosting of your cast bullets, you may have to consider the use of a lead and tin mix and avoid antimony all together. It will not be cheap to do that. Dusty

[JonB_in_Glencoe]

I cast a new batch using straight wheel weights and what little that was in the bottom of the pot from the last time. I tried to keep temp at 650 with some success, but thermometer flops around too much to stay accurate. Back to the cast bullets, They all dropped out of the mould looking nice, no frost, shiny and good bands and grooves. I checked hardness a day later and they are 9 BHN according to my STS dial tester. I gas checked and sized them and noticed that they were under sized, .457 instead of .459. Is this normal with straight wheel weights? I have always used Lyman #2 as a starting point , but am not very experienced. This is the first time under sized bullets came out of this mould for me. I powder coated them and will size them again, hopefully they will have better contact with the .459 sizing bushing.
What causes a casting to be under sized? Is it the mix?

A bit more info would help getting you some good answers.

First, it's time to get that thermometer mounted so it doesn't flop around and gives you a good temperature reading.

Are your straight wheel weights, 100% clip-on style, or a mix of clip-on and Stick-on?

you said, the bullets looked "nice, no frost, shiny and good bands and grooves" Were the edges of the bands crisp? or slightly rounded?

you said, "noticed that they were under sized, .457 instead of .459". Did you measure unsized boolits from previous batches? Did you measure any unsized boolits from this last batch? what is your measuring procedure? I assume you are using a 0-1" Micrometer with correct techniques, are you measuring the samples on each side of the parting line to see if they are out-of-round ?

[44Blam]

So, the thing I found with casting is that the bigger the boolit I am casting the slower the cadence I cast at. I've got a 90 grain 30 cal mold that you have to race to keep everything warm. Then my .40 mold is constant movement and it doesn't really get too hot. Then I've got a 44 mag mold that I have to wait between drops. Usually, those get a little frosty and I noticed that the frosty ones are a little bigger and heavier. Then I've got some 45 caliber molds that are in the 3-400 grain range. I take my time with those and make sure to have good pressure when filling the cavities. I cast until it is hot and then cast, leave open and just go slow.
EDIT:
My 45 caliber molds are Accurate and NOE molds. I size to .460 because my Marlin likes them a little bigger...

[odette]

my previous casting with this mould dropped .460 to .461 bullets measured at the 1st band from the gas check groove. I measured the band, turned the bullet 1/4 turn and remeasured. Then I measured across the length bullet from bottom band to top band and again turned and remeasured. I use a micrometer for measuring. My previous cast was last fall with this mold and I used 9 lbs wheel weights and 2 lbs linotype and got the .460 to .461 dia bullets. They were kind of hard for me to size thru my NOE size bushing on a Lee Turret Classic press, so I sprayed them lightly with a lanolin alcohol mix. I spray then down with break cleaner and wash in hot water and dishsoap to get the lube off, dry and gas check & size them. I then powder coat and size again a day or 2 later.
I did not know about the BHN changes about 3 weeks after casting. I ask for advice at the local gunshops about casting and they tell me that know one does that anymore and very few reload anymore, so I rely on grandpas notes and the nice gentlemen here

[odette]

my old Lyman Mag 20 has seen it's better days. The paint is peeled off the top and it some times doe not turn on. Does anyone use the RCBS Pro Melt 2 or the Lyman Mag 25 Digital. Are they accurate and hold the displayed temperature well.